Apr. 9, 1917 
Water-Retaining Capacity of Soil 
47 
A similar experiment was conducted with the silt-loam surface soil, D, 
which is rich in organic matter and has a hygroscopic coefficient of 10.2, 
and so is in sharp contrast with the residual subsoil J, practically devoid 
of organic matter and having a hygroscopic coefficient of only 5.6. The 
cylinders were similar to those used with J. Two, No. I and II, were 
filled with soil D, containing 24.4 per cent, and the others, No. Ill and IV, 
with the same soil, carrying 30.6 per cent of water. All were left with a 
compact surface for 11 weeks. 
The losses of moisture in the former were confined chiefly to the surface 
foot, the final ratios in the second and third feet being 2.1 and 2.2, respect¬ 
ively, as compared with the initial ratio of 2.4. In the case of the two 
cylinders with the moister soil, with an initial ratio of 3.0, there was a 
distinct loss from all depths, the final ratio in the second and third feet 
being 2.4 and 2.5, respectively. The ratio in the upper half of a 12-inch 
column of this soil, to the surface of which in an air-dry condition 2 or 3 
inches of water had been applied, after which it had been allowed to 
stand for 47 days, protected from evaporation, lay between 2.4 and 3.0 
(Table X). 
DISTRIBUTION OF MOISTURE WHEN EQUILIBRIUM HAS BEEN 
ATTAINED AFTER ADDING WATER TO THE SURFACE OF A COLUMN 
WHOSE MOISTURE CONTENT IS APPROXIMATELY EQUAL TO THE 
HYGROSCOPIC COEFFICIENT 
In this experiment we used all 13 soils mentioned in Table I. In the 
case of each soil two galvanized-iron cylinders 2 feet long, 4 inches in 
diameter, and provided with bottoms and tight-fitting covers, were filled, 
as described above, with the soil having a moisture content approximately 
equal to the hygroscopic coefficient. To permit the escape of air as the 
water was being added, small holes had been made in the bottoms. The 
soil was tamped in until even with the rim, smoothed off, and covered 
with a metal tray, which was left on until all the cylinders had been filled. 
In the case of each of the soils, except the dune sand Q, the initial water 
content was approximately equal to the hygroscopic coefficient and the 
amount of water added to the surface was sufficient to raise the average 
moisture content of all the soil in the cylinder to 1.5 times the hygro¬ 
scopic coefficient, it varying according to the soil and the initial moisture 
content of this from 0.27 inch to 2.12 inches. To the sand Q, which was 
in an air-dry condition, the added water amounted to 0.5 inch in two 
cylinders and to 1.0 inch in two others. 
To make more uniform the initial penetration of the water, the cylin¬ 
ders used were inverted in the flat-bottomed metal trays, the desired 
amount of water then added and allowed to rise into the soil by capillarity 
until all or nearly all had been absorbed, after which they were placed 
right side up. Where with the coarsest soils a few drops of water re¬ 
mained in the tray, these were added to the surface after the cylinder had 
